you get sardines mainly from packs after beating a certain difficulty and I recommend you use steam to play the game (it's free).
alternatively if your ok with restarting your game entirely from a save wipe you could use the getinline code, reset your game and enter it again, you get around 1000 sardines a minute, and you'll be able to get everything you need incredibly quickly, and if you still don't want to do that we have profiles in the discord that allow you to just load em up and play the run.
You can also beat a payload run and alt f4 after opening the cards then reopen and go to that save and it immediately gives another set of cards
Also what blava’s saying works but you have to reset your file for that and that method doesn’t ’ give you unlocks for parts
The getinline code wont work for me I'm playing on https://flashmuseum.org/learn-to-fly-3/